The present invention relates to fuses and more particularly to automotive fuses.
Automotive fuses, such as blade type fuses are known in the art. Modern electrical blade fuses have been manufactured by Littelfuse, Inc., the assignee of the present invention. Blade fuses protect electrical automotive circuits from current overloads. The protection results from the creation of an opening of a fuse element of the fuse, and therefore in the circuit protected by the fuse. Upon a current overload of a certain magnitude and over a predetermined length of time the fuse element or link breaks or opens.
Blade fuses are used extensively in automobiles. Automobile manufacturers are constantly looking for ways to reduce costs as much as possible. Manufacturers strive to reduce costs, such as material and manufacturing costs, as much as possible. Automobile manufacturers on the other hand are constantly adding more electrical devices and accessories to automobiles. Consequently, automobile circuits having increasingly higher operating voltages. Sixty volt systems for example, are being contemplated and implemented. Higher ratings require more robust conductive elements and more insulation. The trend towards saved rather than lower cost therefore competes against the trend towards higher capacity.
Known blade fuses employ: (i) an insulative housing; (ii) conductive male terminals that fit into female terminals extending from the automobile's fuse block; and (iii) a fuse element connecting the male terminals. The male terminals have typically extended below the insulative housing. When installed in the fuse block, the housing of the fuse sits above the female terminals. The housing in such configuration and placement provides a convenient apparatus or area of the fuse to be grasped and pulled or pushed to remove or replace the fuse, respectively.
In known blade-type fuses, the upper portions of the male terminals, which reside within the housing, provide suitable places to which to secure the insulative housing to the terminals or metal portions of the fuse. Because the upper parts of the terminals sit above the fuse block, the upper parts can be used to define holes, for example, through which the housing is anchored. One common process for attaching the insulative housing to the metal terminals is called a “staking” process. In a heat staking process, heat is applied to the housing at points overlapping or aligned with the holes in the terminals. The applied heat melts or deforms the insulative housing so that the insulative material flows into the holes, hardens and thereafter holds the housing and the terminals together. Another staking method is commonly called a “cold stake”, in which the material is deformed by mechanical force alone. No heat is used.
Recently, attempts have been made to reduce the amount of metal in blade-type fuses by eliminating the upper parts of the male terminals so that the resulting fuse fits primarily in between the female terminals of the fuse block and not significantly above the female terminals. One such “low profile” blade fuse is disclosed in U.S. Pat. No. 6,359,543. The fuse disclosed therein includes a housing that covers the top of the terminals but enables the outer sides of the terminals to be exposed. The exposed surfaces of the terminals are mated with the female terminals of the fuse block.
One concern facing all blade-type fuses arises when the fuse element opens. The opening of the fuse element coincides with a release of energy, including sound and heat. The air within the housing expands, placing stress on the housing and the attachment mechanisms holding the housing to the terminals. In certain instances if the housing is not properly attached to the terminals, the housing upon a short circuit can come free from the terminals or otherwise become difficult to remove from the fuse block.
The “low profile” fuse, while reducing the amount of metal and insulating material for a given rating, makes insertion and removal more cumbersome because there is less material exposed to grasp. Further, the reduced metal and insulative material reduces the area of overlap between the metal and the insulative material, making the staking or attachment process more difficult and less effective. The housings of known “low profile” fuses may therefore be more susceptible to dislodgement upon opening, creating a situation in which it is difficult to remove the male terminals of the fuse, which are friction fitted to the female terminals of the fuse block. This is especially true in the case of the “low profile” fuse because the male terminals do not extend significantly above the female terminals of the fuse block.
A need therefore exists for a “low profile” type fuse having a housing more securely attached to the terminal portions of the fuse to reduce the likelihood that the housing will become dislodged from the terminals when the fuse element opens.
A further need exists for a “low profile” type fuse that is readily removeable from the fuse block after an overcurrent condition occurs and the element opens.